Abstract: Devised are a glass and glass substrate, which contain an alkaline component at a low content, are low in density and thermal expansion coefficient, are high in strain point and Young's modulus, and are excellent in devitrification resistance, meltability, formability, and the like. That is, the glass of the present invention includes as a glass composition, in terms of mass %, 58 to 70% of SiO2, 16 to 25% of Al2O3, 3 to 8% of B2O3, 0 to 5% of MgO, 3 to 13% of CaO, 0 to 6% of SrO, 0 to 6% of BaO, 0 to 5% of ZnO, 0 to 5% of ZrO2, 0 to 5% of TiO2, and 0 to 5% of P2O5.

Abstract: In an annealing zone (3) of a glass sheet producing method, a curved portion (5) is formed by curving a glass ribbon (G) in a width direction, and a concavo-convex direction in a front and back direction of the curved portion (5) is reversed at least between an upper side and a lower side of a part of a region in the width direction of the glass ribbon (G). Therefore, a bending resistance in an upper and lower direction of the glass ribbon (G) and a bending resistance in the width direction of the glass ribbon (G) are increased.

Abstract: The optical communication device substrate according to the present invention includes one of ceramic and glass ceramic each having an average thermal expansion coefficient of ?55 to ?120×10?7°/C. in the temperature range of ?40 to +100°C. and each containing one of a ?-quartz solid solution and a ?-eucryptite solid solution as a main crystal. In the substrate, maximum thermal expansion hysteresis that occurs when temperature rise from ?40°C.to 100°C. at a rate of 1°C./min and temperature lowering from ?100°C.to ?40°C. at a rate of 1°C./min are performed is less than 12 ppm.